In general, compressors may be classified into a rotating type and a reciprocating type according to a method of compressing a refrigerant. The rotating type compressor varies a volume of a compression chamber while a piston performs a rotary or orbiting motion in a cylinder. The reciprocating type compressor varies a volume of a compression space while a piston performs a reciprocal motion in a cylinder. A rotary compressor which compresses a refrigerant while a piston rotates using rotational force of a driving motor is well known as one of the rotating type compressor.
The rotary compressor compresses a refrigerant by using a rolling piston which performs an eccentric rotary motion in a compression space of a cylinder, and a vane which comes in contact with an outer circumferential surface of the rolling piston so as to divide the compression space of the cylinder into a suction chamber and a compression chamber. In recent time, a capacity-variable rotary compressor of which a refrigerating capacity is variable according to changes in loads is introduced. A technology of applying an inverter motor and a technology of varying a volume of a compression chamber by bypassing some of compressed refrigerant out of a cylinder are known as technologies for varying a refrigerating capacity of a compressor. However, for applying the inverter motor, a production cost of a compressor increases because a price of a driver for driving the inverter motor is extremely higher than that of a typical constant speed motor. On the other hand, for applying a refrigerant bypassing method, a piping system is made complicated, which increases flow resistance of the refrigerant and lowers efficiency of a compressor.
Also, in the rotary compressor, since a compression space is formed by the rolling piston and the vane, a degree that the rolling piston and the vane are closely adhered to each other is closely related to compressor efficiency. That is, when the rolling piston and the vane are spaced from each other, a refrigerant of a compression chamber may be leaked into a suction chamber to cause a compression loss, the vane may be jumped with respect to the rolling piston, thereby increasing compressor noise. On the other hand, when the rolling piston and the vane are excessively adhered to each other, a frictional loss may occur between the rolling piston and the vane. Taking into such problems account, a method has been known in the related art, as illustrated in FIG. 1, in which a hinge recess 3a is formed on an outer circumferential surface of a rolling piston 3, which is coupled to an eccentric portion 2a of a rotation shaft 2 in a compression space 1a of a cylinder 1 so as to perform an eccentric rotary motion, and a hinge protrusion 4a is formed on an end portion of a vane 4 which is slidably coupled to a vane slot 1b of the cylinder 1, such that the hinge protrusion 4a of the vane 4 is coupled to the hinge recess 3a of the rolling piston 3 to be rotatable within a predetermined angle. The related technology is disclosed in Japanese Patent Registration No. 2815432 (Name of the Invention: Rotary compressor).
However, in the related art rotary compressor, as a bearing surface of the hinge protrusion 4a is formed with an angle of circumference (or a circumferential angle) of 180° or more, an object to be processed (i.e., the hinge protrusion) is difficult to be in position while cutting and grinding the bearing surface of the hinge protrusion 4a, and accordingly should be machined in a special manner. This results in causing a difficulty in producing the hinge protrusion 4a of the vane 4 and increasing a machining cost.
In addition, in the related art rotary compressor, most of an outer circumferential surface of the hinge protrusion 4a is formed in a curved surface which mostly requires for high precision, which lowers a machining degree. Accordingly, interference is caused between the rolling piston 3 and the vane 4, which brings about an unstable behavior of the rolling piston 3 or the vane 4, resulting in lowering compression efficiency.